Heretofore, others have suggested various gate arrangements for controlling the gravity discharge of free flowing or fluid bulk material from containers such as the holds of a bulk cargo ship. U.S. Pat. Nos. 3,990,588 and 4,004,700 show hoppered bottom ships, wherein the flow of material from each hopper is controlled by a pair of gates supported by rollers which run on horizontal parallel tracks. In order to have proper control of the rate of discharge, it is desirable to synchronize the opening and closing of the gates. U.S. Pat. No. 4,009,906 illustrates a metering gate for a fluid bulk material hopper wherein a motion balancing mechanism interconnects a pair of closure panels for equalizing the distances through which the panels are displaced by a drive mechanism. A lag elimination mechanism is utilized so that each portion of each panel is displaced in equal amounts as the closure panels are opened and closed by the drive mechanism. The synchronizing of a pair of elevator door panels is achieved by a sprocket and chain arrangement in U.S. Pat. No. 1,198,896.